This is a counterpart application of a Japanese patent applications 2000-102619, filed on Apr. 4, 2000, 2000-251885, filed on Aug. 23, 2000, and 2000-342660, filed on Oct. 3, 2000, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a multi-electron-beam exposure apparatus, a multi-axis electron lens, a fabrication method of the multi-axis electron lens and a fabrication method of a semiconductor device.
2. Description of the Related Art
Conventionally, it is known an electron-beam exposure apparatus capable of exposing a wafer with a plurality of electron beams in order to form a semi-conductor device. For example, an electrons-beam exposure apparatus including an electron lens having a pair of magnetic plates placed in parallel relationship with each other is disclosed in U.S. Pat. No. 3,715,580 or in U.S. Pat. No. 4,209,702. The pair of magnetic plates has a plurality of through holes at places corresponding to each other for respectively having the plurality of electron beams pass therethrough in order for focusing images.
As semi-conductor devices are becoming more and more minute structures, exposure apparatuses for forming lines of the semi-conductor devices are required to have high accuracy in focusing images. Therefore, it is highly expected that an electron-beam exposure apparatuses capable of exposing a plurality of electron beams for forming patterns of lines of the semi-conductor devices be commercially produced. In order to produce quantity of semi-conductor devices by such the electron-beam exposure apparatus, preferably, the focusing points of the plurality of electron beams should be adjusted on the wafer become.
The conventional electron beam exposure apparatus disclosed in above patents corrects the focusing point of the electron beams by using exciting coils provided between the pair of magnetic plates. However, as for the conventional electron beam exposure apparatus, in case that the magnetic fields formed in each of the plurality of through holes are dispersed largely, it is difficult to correct the focusing point of the electron beams uniformly. Especially, as the size of the wafer becomes lager, the electric field strength formed in the through holes at the edge of the electron lens becomes more different from that at the center of the electron lens.
Therefore, as for the conventional electron beam exposure apparatus, the focusing points of the plurality of electron beams cannot be adjusted on the wafer. Thus, this type of electron-beam exposure apparatus cannot show accuracy in focusing the images. This fact prevents the electron-beam exposure apparatus exposing a plurality of electron beams from commercially produced.
Therefore, it is an object of the present invention to provide a multi-beam exposure apparatus using a multi-axis electron lens, a multi-axis electron lens and a fabrication method of a semiconductor device, which is capable of overcoming the above drawbacks accompanying the conventional art. The above and other objects can be achieved by combinations described in the independent claims. The dependent claims define further advantageous and exemplary combinations of the present invention.
According to the first aspect of the present invention, an electron beam exposure apparatus for exposing a wafer with a plurality of electron beams, comprising a multi-axis electron lens having a plurality of lens openings operable to converge said plurality of electron beams independently of each other by allowing said plurality of electron beams to pass therethrough, respectively, said plurality of lens openings having different shapes.
The multi-axis electron lens may include a plurality of magnetic conductive members having a plurality of openings arranged to be substantially parallel to each other, said plurality of openings forming said lens openings.
The magnetic conductive members may include said openings having different sizes.
At least one of said plurality of magnetic conductive members may include cut portions provided in outer peripheries of said openings.
The cut portions may have different sizes.
At least one of said magnetic conductive members may include a magnetic conductive projection provided on a surface thereof between a predetermined one of said openings and another opening adjacent to said predetermined opening, said magnetic conductive projection projecting from said surface of said at least one of said magnetic conductive members.
The electron beam exposure apparatus may further comprise a lens-intensity adjuster including: a substrate provided to be substantially parallel to said multi-axis electron lens; and a lens-intensity adjusting unit, provided on said substrate, operable to adjust the lens intensity of said multi-axis electron lens applied to said electron beams passing through said lens openings, respectively.
The lens-intensity adjusting unit may include an adjusting electrode provided to surround said electron beams from said substrate to said lens opening, said adjusting electrode being insulated from said magnetic conductive members.
The lens-intensity adjusting unit may include a plurality of adjusting electrodes provided to surround said electron beams, respectively, from said substrate to said lens opening.
The lens-intensity adjusting unit may further include a means operable to apply different voltages to said plurality of adjusting electrodes.
The lens-intensity adjusting unit may further include an adjusting coil operable to adjust magnetic field intensities in said lens openings, said adjusting coil being provided to surround said electron beams from said substrate along a direction in which said electron beams are radiated.
The multi-axis electron lens may further include a non-magnetic conductive member having a plurality of through holes, said non-magnetic conductive member being provided between said plurality of magnetic conductive members, said plurality of openings of said magnetic conductive members and said plurality of through holes forming together said plurality of lens openings.
The multi-axis electron lens may further include a coil part having a coil provided in an area surrounding said magnetic conductive members for generating a magnetic field and a coil magnetic conductive member provided in an area surrounding said coil.
The coil magnetic conductive member may be formed from a material having a different magnetic permeability from that of a material for said plurality of magnetic conductive members.
The electron beam exposure apparatus may further comprise at least one further multi-axis electron lens operable to reduce cross sections of said electron beams.
The electron beam exposure apparatus may further comprise an electron beam shaping unit that comprises: a first shaping member having a plurality of first shaping openings operable to shape said plurality of electron beams; a first shaping-deflecting unit operable to deflect said plurality of electron beams after passing through said first shaping member, independently of each other; and a second shaping member having a plurality of second shaping openings operable to shape said plurality of electron beams after passing through said first shaping-deflecting unit to have desired shapes.
The electron beam shaping unit may further include a second shaping-deflecting unit operable to deflect said plurality of electron beams deflected by said first shaping-deflecting unit independently of each other toward a direction substantially perpendicular to a surface of said wafer onto which said electron beams are incident, wherein said electron beam shaping unit allows said plurality of electron beams deflected by said second shaping-deflecting unit to pass through said second shaping member so as to shape said electron beams to have said desired shapes.
The second shaping member may include a plurality of shaping-member illumination areas onto which said electron beams deflected by the second shaping-deflecting unit are incident, and said second shaping member includes said second shaping openings and other openings having different sizes from sizes of said second shaping openings in said shaping-member illumination area.
The electron beam exposure apparatus may further comprise: a plurality of electron guns operable to generate said plurality of electron beams; and a further multi-axis electron lens operable to converge said plurality of electron beams generated by said plurality of electron guns to make said converged electron beams incident on said first shaping member, wherein said first shaping member divides said electron beams after passing through said further multi-axis electron lens.
The electron beam exposure apparatus may comprise a plurality of multi-axis electron lenses having said lens openings.
The multi-axis electron lens may further include a plurality of dummy openings through which no electron beam passes.
The plurality of dummy openings may be provided in outer peripheries of an area where said plurality of lens openings are arranged.
According to the second aspect of the present invention, an electron lens for converging a plurality of electron beams independently of each other, comprising a plurality of magnetic conductive members arranged to be substantially parallel to each other, said magnetic conductive members having a plurality of openings, wherein said plurality of openings of said magnetic conductive members form a plurality of lens openings allowing said plurality of electron beams to pass therethrough, respectively, to converge said electron beams independently of each other, said lens openings having different shapes.
According to the third aspect of the present invention, a fabrication method of a semiconductor device on a wafer, comprising: performing focus adjustments for said plurality of electron beams independently of each other by using a multi-axis electron lens having a plurality of lens openings having different shapes that allow a plurality of electron beams to pass therethrough, respectively, to converge said electron beams independently of each other; and exposing a pattern onto said wafer by illuminating said wafer with said plurality of electron beams.
The summary of the invention does not necessarily describe all necessary features of the present invention. The present invention may also be a sub-combination of the features described above The above and other features and advantages of the present invention will become more apparent from the following description of the embodiments taken in conjunction with the accompanying drawings.